US Day 3-7 Hazards Outlook
NWS Weather Prediction Center College Park MD
430 PM EDT Wed Jul 14 2021
 
Valid Saturday July 17 2021 - Wednesday July 21 2021
 
Hazards:
- Heavy rain across portions of the interior northern Mid-Atlantic, Sat-Sun, Jul 17-Jul 18.
- Heavy rain across portions of the Gila Mountains in eastern Arizona, Sat-Wed, Jul 17-Jul 21.
- Flooding possible across portions of the Middle Mississippi Valley, and the Upper Midwest.
- Flooding occurring or imminent across portions of northern Florida, the Middle Mississippi 
Valley, and eastern Texas.
- Excessive heat across portions of the northern Rockies and the northern Great Basin, Sun-Mon, Jul 
18-Jul 19.
- Excessive heat across portions of the Northern Plains, Sat-Tue, Jul 17-Jul 20.
- Much above normal temperatures from across portions of the central and northern Great Basin, the 
northern to central Rockies, across the northern Plains, and into the Upper Midwest, Sat-Wed, Jul 
17-Jul 21.
 
Detailed Summary:

During the medium range forecast period (Saturday, July 17th to Wednesday, July 21th), an 
upper-level trough settling across the Great Lakes and the Northeast will extend a cold front 
southwestward into the central Plains.  The front is forecast to gradually push through the central 
U.S., then into the East Coast and across the Deep South by the middle of next week.  Model 
guidance continues to indicate the likelihood of moderate rainfall ahead of this slowly advancing 
front but with a fair amount of uncertainty regarding if and where low pressure waves may form and 
develop along the front.  The development of these frontal waves will be important in determining 
if and where heavier rainfall and thunderstorms will be triggered.  No heavy rain areas are 
indicated across much of the central and eastern U.S. as well as the Deep South due to generally 
moderate rainfall amounts predicted along with a steady forward motion of the rain.  However, areas 
of heavy rainfall are possible especially near where low pressure waves form near the front, along 
with the possibility of mesoscale convective systems that may form in the Deep South ahead of the 
front toward the middle of next week.  Nevertheless, portions of the interior Mid-Atlantic appear 
to be more susceptible to heavy rain associated with afternoon to early evening thunderstorms near 
a pre-frontal lee trough during the weekend.

Over the southern Rockies into the Desert Southwest, monsoonal moisture will keep a good chance of 
showers and afternoon/early evening thunderstorms through the medium-range period.  Most areas 
should see rainfall below hazard levels at this time but the upslope portion of the Gila Mountains 
in eastern Arizona appears to be under the highest threat of heavy rain through the middle of next 
week when models indicate an increasing influx of the moisture from the south.

Meanwhile, the heatwave is expected to continue from the central and northern Great Basin eastward 
across the northern Plains and into the upper Midwest under a persistent upper ridge through much 
of the medium range period.  The highest temperature anomalies are expected over the northern High 
Plains, where high temperatures into the triple digits are forecast through midweek next week.  
Excessive heat is indicated for this area.  Excessive heat is also indicted along the Snake River 
valley and parts of the northern Rockies Sunday and Monday when the heat is forecast to be most 
intense.  In addition, much of the Dakotas, northeast Wyoming, and the western half of Minnesota 
are experiencing severe to exceptional drought that will likely worsen due to the persistent heat 
and lack of rain.

For Alaska, a general increase in rain chances is expected for the western portions of the state by 
early next week as a series of occluded cyclones is forecast to steadily move into the Bering Sea.  
By midweek, models are indicating the possibility of moderate to perhaps heavy rain to reach 
southwestern Alaska ahead of a stronger occluded cyclone.  However, no heavy rain areas are 
indicated for now due to a fair amount of uncertainty together with rainfall amounts generally less 
than 1.5 inches.

Kong